Microinverter systems and subsystems

ABSTRACT

An alternating current (AC) module system includes branch circuits and a main service panel to receive power from the branch circuits. A photovoltaic (PV) supervisor is located between the branch circuits and the panel. The PV supervisor aggregates the power from the branch circuits. The PV supervisor also performs a nonredundant operational function for one or more of the branch circuits. The PV supervisor includes a gateway device to permit control of the operational functions.

BACKGROUND

Photovoltaic (PV) cells, commonly known as solar cells, are devices forconversion of solar radiation into electrical energy. Generally, solarradiation impinging on the surface of, and entering into, the substrateof a solar cell creates electron and hole pairs in the bulk of thesubstrate. The electron and hole pairs migrate to p-doped and n-dopedregions in the substrate, thereby creating a voltage differentialbetween the doped regions. The doped regions are connected to theconductive regions on the solar cell to direct an electrical currentfrom the cell to an external circuit. When PV cells are combined in anarray such as a PV module, the electrical energy collected from all ofthe PV cells can be combined in series and parallel arrangements toprovide power with a certain voltage and current.

Module-level power electronics (MLPE) serve and support PV cells and PVsystems. MLPEs may include microinverters and system supervisors orcontrollers. Microinverters provide certain features in these multi-partsystems, particularly when used in an alternating current (AC) module.Microinverters themselves may include several subsystems to accomplishthe functionality needed to provide these features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an alternating current module system having aphotovoltaic supervisor/controller as may be employed in embodiments.

FIG. 2 illustrates a microinverter for a photovoltaic module as may beemployed in embodiments.

FIG. 3 illustrates a photovoltaic supervisor/controller as may beemployed in embodiments.

FIG. 4 illustrates a flowchart for generating power within an AC modulesystem as may be employed in embodiments.

FIG. 5 illustrates a photovoltaic supervisor/controller connected tophotovoltaic modules as may be employed in embodiments.

FIG. 6 illustrates a photovoltaic supervisor/controller connected tophotovoltaic modules as may be employed in embodiments.

FIG. 7 illustrates a photovoltaic supervisor/controller connected tophotovoltaic modules as may be employed in embodiments.

FIG. 8 illustrates a photovoltaic supervisor/controller connected tophotovoltaic modules as may be employed in embodiments.

FIG. 9 illustrates a photovoltaic supervisor/controller connected tophotovoltaic modules as may be employed in embodiments.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature andis not intended to limit the embodiments of the subject matter of theapplication or uses of such embodiments. As used herein, the word“exemplary” means “serving as an example, instance, or illustration.”Any implementation described herein as exemplary is not necessarily tobe construed as preferred or advantageous over other implementations.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,brief summary or the following detailed description.

This specification includes references to “one embodiment” or “anembodiment.” The appearances of the phrases “in one embodiment” or “inan embodiment” do not necessarily refer to the same embodiment.Particular features, structures, or characteristics may be combined inany suitable manner consistent with this disclosure.

Terminology. The following paragraphs provide definitions and/or contextfor terms found in this disclosure (including the appended claims):

“Comprising.” This term is open-ended. As used in the appended claims,this term does not foreclose additional structure or steps.

“Configured To.” Various units or components may be described or claimedas “configured to” perform a task or tasks. In such contexts,“configured to” is used to connote structure by indicating that theunits/components include structure that performs those task or tasksduring operation. As such, the unit/component can be said to beconfigured to perform the task even when the specified unit/component isnot currently operational (e.g., is not on/active). Reciting that aunit/circuit/component is “configured to” perform one or more tasks isexpressly intended not to invoke 35 U.S.C. §112, sixth paragraph, forthat unit/component.

“First,” “Second,” etc. As used herein, these terms are used as labelsfor nouns that they precede, and do not imply any type of ordering(e.g., spatial, temporal, logical, etc.). For example, reference to a“first” solar cell does not necessarily imply that this solar cell isthe first solar cell in a sequence; instead the term “first” is used todifferentiate this solar cell from another solar cell (e.g., a “second”solar cell). Likewise, a first PV module does not necessarily imply thatthis module is the first one in a sequence, or the top PV module on apanel. Such designations do not have any bearing on the location of thePV module, substrings, and the like.

“Based On.” As used herein, this term is used to describe one or morefactors that affect a determination. This term does not forecloseadditional factors that may affect a determination. That is, adetermination may be solely based on those factors or based, at least inpart, on those factors. Consider the phrase “determine A based on B.”While B may be a factor that affects the determination of A, such aphrase does not foreclose the determination of A from also being basedon C. In other instances, A may be determined based solely on B.

“Coupled”—The following description refers to elements or nodes orfeatures being “coupled” together. As used herein, unless expresslystated otherwise, “coupled” means that one element/node/feature isdirectly or indirectly joined to (or directly or indirectly communicateswith) another element/node/feature, and not necessarily mechanically.

“Inhibit”—As used herein, inhibit is used to describe a reducing orminimizing effect. When a component or feature is described asinhibiting an action, motion, or condition it may completely prevent theresult or outcome or future state completely. Additionally, “inhibit”can also refer to a reduction or lessening of the outcome, performance,and/or effect which might otherwise occur. Accordingly, when acomponent, element, or feature is referred to as inhibiting a result orstate, it need not completely prevent or eliminate the result or state.

In addition, certain terminology may also be used in the followingdescription for the purpose of reference only, and thus are not intendedto be limiting. For example, terms such as “upper”, “lower”, “above”,and “below” refer to directions in the drawings to which reference ismade. Terms such as “front”, “back”, “rear”, “side”, “outboard”, and“inboard” describe the orientation and/or location of portions of thecomponent within a consistent but arbitrary frame of reference which ismade clear by reference to the text and the associated drawingsdescribing the component under discussion. Such terminology may includethe words specifically mentioned above, derivatives thereof, and wordsof similar import.

In the following description, numerous specific details are set forth,such as specific operations, in order to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to one skilled in the art that embodiments of the presentdisclosure may be practiced without these specific details. In otherinstances, well-known techniques are not described in detail in order tonot unnecessarily obscure embodiments of the present disclosure.

Embodiments may include a multi-component system with one or severalgroups of peer components and one or more supervisors or controllers.There may be several groups of peer components where each group providessimilar or identical services for the system as a whole and likewiseoffers similar or identical features to the system or other user. Theremay also be one or more supervisors or controllers serving to managethese groups of peer components and provide interface between the systemand external components and users. Communication among and between thepeers in a group, among and between peers of different groups, and amongand between the groups and the one or more supervisors or controllersmay use isolated dedicated communication lines as well as powerconnections.

In embodiments, redundant functionality offered by peers in a singlegroup or from several groups may be consolidated in one or morelocations and removed or less frequently employed in the peers, groupsor other components. This hybrid approach, by reducing redundancy ofcertain features and consolidating how the features may be provided anddeployed may be advantageous for various reasons. These may includeeliminating unnecessary redundancy, centralizing components for serviceand repair; centralizing communications; and being able to provide morerobust designs because of a centralized topology and its associatedelimination of unused backup or other subsystems.

Embodiments may involve PV systems and their components and subsystems.The components may include PV supervisors or controllers as well as PVmodules with microinverters. The hybrid approach may include combiningand eliminating various subsystems in both the PV supervisors orcontrollers and the microinverters. These subsystems can include and/orprovide input stages and output stages, housekeeping power supplies,communications, output filters, surge protection, chassis protection,and cabling. Other subsystems and components may also be eliminated,combined, and/or centralized in embodiments.

In some embodiments, PV module(s), where a module is one or more modulespaired with a single microinverter, may be connected within a system toa photovoltaic (PV) supervisor/controller. This combination may provideor enhance electrical balance of system components, such as overcurrentprotection, into a panel including the supervisor/controller that may beelectrically connected between an array of AC modules, where a module isone or more modules paired with a single microinverter and the powergrid service connection. In addition to the balance of systemcomponents, embodiments may be configured to consolidate somemicroinverter functions into the supervisor/controller or elsewhere inthe system.

Some embodiments may segregate functions between the module-level, orother distributed electronics, and the supervisor/controller. In manysystems, the electronics will be distributed across a PV module array aswell as centralized at or near the main service panel. There may also bea balance of system components. Thus, embodiments may serve to developan improved partitioning of functions between the distributed,centralized, and a balance of system components.

Microinverters according to some embodiments may include or share thefollowing subsystems. An input stage may convert direct current (DC)power from the solar panel or other DC source to a high voltage (˜400V)dc bus, usually with electrical/transformer isolation and may alsoconduct maximum power point tracking (MPPT). An output stage may convertthis high voltage to a grid compatible AC current and may also regulatethe bus voltage as a desired set point value. One or more housekeepingpower supplies provide a low level of power to logic and controlcircuitry. These housekeeping power supplies (typically <1 W) may besmall power supplies to provide stable voltage rails to logic andcontrol circuitry and there may be more than one supply in embodiments,with each having more than one output voltage. Communication circuitsmay provide communications to and from the PV supervisor/controller withsome employing power line carrier functionality. Microcontrollers anddigital signal processors may provide the control functions, which mayinclude dynamic regulation of signals and regulatory functions. Filtersmay reduce electrical distortion on the AC output and may includepassive components such as inductors and capacitors, which can serve toreduce electrical distortion on the AC output of a microinverter. Thisdistortion may be in the form of low frequency distortion (IEEE 1547,for example), harmonics, or high frequency distortion (FCC part 15, forexample). Surge protection may also be included. This surge protectionmay include topology being directly coupled to or partially embeddedwith an output filter with durability suitable to survive thousands ofvoltages in excess of normal line voltage. Metal-oxide varistors may beemployed in embodiments to provide surge protection. A chassis housingthe electronics and providing mounting and/or installation features;and, one or more cables connecting the microinverter to peers, othercomponents of the system, e.g., a connection to the PVS, and forreceiving DC input, may be included as well.

Some embodiments include microinverters having an active filter stage toreplace the high voltage DC bus configuration. These microinverters mayalso include an AC link transformer. As power is generated by the solarpanel in the PV module, the microinverter converts it into AC currentusing some or all of these components.

In some embodiments, a service panel may connect to the differentmicroinverters within the PV modules through the PVsupervisor/controller. The supervisor/controller may include gatewayfunctions with overcurrent protection and branch circuit aggregation.Data may be communicated via power line carriers (PLC) to and from thePV modules. Data communication may be exchanged with servers using agateway device, for example, via the Internet. The gateway device may becoupled with wires or a wireless service to the server. For example, thegateway device may connect to the server using a homeowner's router viahardware or WiFi.

In other embodiments, surge protection is removed, or significantlyreduced, in each microinverter while adding a surge suppressor to the PVsupervisor/controller. Surge suppressors may be placed into subpanels asa matter of practice or necessity to protect the PV modules, especiallyin locales having an increased incidence of lightening. As such, thesurge suppressor within the supervisor/controller may be a replacementof an existing component or redesign of that component. Beingpreinstalled in the supervisor/controller may save effort for the systeminstaller. Each microinverter may have sufficient surge suppression toprotect the line, so that a plurality of microinverters may offer overlyredundant surge protection. In some embodiments, this redundancy may bereduced or eliminated.

The disclosed system may also combine high-speed communication lineswith the AC cables leading to the microinverters. This combination maybe achieved with or without the surge suppressor in thesupervisor/controller. Communication wires may be bundled with the ACpower wires within each microinverter cable. Further, drop cables from arooftop may be run alongside the communication wires. This may be analternative to PLC, which may be susceptible to line noise and numeroustroubleshooting tasks. Because the termination of the AC cables is atthe PV supervisor/controller, embodiments may terminate thecommunication wires within the same enclosure.

A physical layer may be used, which would be largely immune from noiseand conventional PLC troubleshooting. The physical layer may alsoprovide a faster response for communications. Further, it might be morereliable and provide more inherent security. Such a configuration may behelpful in newer applications requiring faster and more reliablecommunications. Other hardwired forms of communication are alsopossible.

The PV supervisor/controller may also deliver power to the PV modulesvia the same hardwired bundle as communications. For example, a powersupply may be placed in the supervisor/controller. The power supply maybe a standalone unit or integrated with the gateway device. Gatewaycircuits may include their own power supply, but it may not be usefulfor powering the PV modules. In some embodiments, the housekeeping powersupplies for the PV modules may be eliminated or significantly reduced,such as to a simple postregulator or point-of-load circuits.

The power provided may be power over the data lines. The redundancy ofpower supplies in microinverters may be eliminated or greatly reduced byhaving a single, higher power supply in the supervisor/controller. Thehigher power supply may be made highly efficient and may be less costsensitive as only one is needed. Further, more space may be available inthe supervisor/controller than in the microinverters for such a powersupply.

In some embodiments, the power supply may be used in specialcircumstances, without substantially altering the power supplies presentin the microinverters. Power supplies in the microinverters may be fedfrom the DC (solar) input and, therefore, operate with thresholddaylight. The power supply based in the PV supervisor/controller may beused as a means to supply power when ample daylight is not present. Itmay power some subcircuits of the microinverters for a small amount ofthe time. These embodiments may be useful to installers attempting tocommission or otherwise communicate with components within the system asthe sun sets or daylight is not available. The power supply does notneed to by particularly efficient, highly performing, or have asubstantial power rating.

In embodiments, a filter may be added to the PV supervisor/controllerand some or all output filter components may be removed from themicroinverters. The aggregate functions may be placed in thesupervisor/controller with the filter aiding in reducing lower frequencydistortion, such as IEEE 1547 harmonics, or higher frequency distortion,such as EMI/FCC electrical noise. The filter may also selectively blocksome frequencies, such as a chosen PLC frequency. Other generators,rather than PV modules, may be connected to the supervisor/controllerthat may or may not communicate via PLC.

One or more sensors may be equipped with the PV supervisor/controller.In some embodiments, two current sensors may be coupled to the outputfilter and the current sensors may be current transformers (CT) or anyother suitable current sensor. Voltage, temperature, and other types ofsensors may be employed in the supervisor/controller. For example, thecurrent sensors may be coupled to the input and the output of thefilter, if one is used in the supervisor/controller. The sensors may beused to monitor PV power production and energy consumption and in someembodiments the sensors may be integrated with the supervisor/controllerand may not require a separate installation.

In addition to PV production, the current sensors may be used to improvethe harmonic performance of the PV module system. For example, it may bedifficult for the microinverters to monitor and correct for distortionbecause they have reduced filtering. The gateway device, however, may beconfigured to sense the collected PV current and, with its processingcapability, calculate the appropriate predistortion or other correctionsignals to be used by the microinverters. These signals may be sent tothe microinverters via the communication lines disclosed above. A widerange of conditions may be addressed using this process.

The current sensors also may be used for current limiting, faultdetection, or otherwise comply with regulatory requirements. Limits onpower output may be required due to net export limitations. Whendetecting a current that is out of range or otherwise unsuitable, the PVsupervisor/controller may cause the microinverters to disable theirpower output, curtail their power, or otherwise alter their behaviorusing the communication wires.

In some embodiments, other generating units aside from PV modules arecoupled to the supervisor/controller, such as gas generators,grid-interactive storage device, and the like. Additional circuitbreakers may be added to accommodate more generators. Any suitableovercurrent protection configuration may be used, particularly becausecircuit breakers are large physically and somewhat expensive. Forexample, a current sensor with detection circuitry may be used to sensean overcurrent. By augmenting some or all of the breaker lines withcontrolled switches, such as relays, the current may be interruptedwithout using a conventional circuit breaker.

In other embodiments, the gateway device may provide the sensing andcalculation necessary to determine the phase angle of the power line.Normally, microinverters employ phased-locked loops (PLL) circuits toperform this function. This feature may be computationally intensive,especially in consideration of highly-distorted line voltages, so it maybe that the computation burden for the microinverters can be reduced byconsolidating the PLL function in the supervisor/controller. Thesupervisor/controller may provide, via the communication wires, asynchronizing signal by which all microinverters would base their ownphase angles.

At a deeper level of synchronization, the high-frequency switchingoutputs of the microinverters may be synchronized, though notnecessarily simultaneous. The converters may require a high-frequencymodulation signal from their output, such pulse width modulation (PWM).

Many inverter topologies use a fixed-frequency modulation, or one thatis fixed for some period of time or under some operating conditions. Insome embodiments, the communication line may coordinate the switching ofmicroinverters to generate overall higher performance or lower costs.For example, if two or more converters are switching at the samefrequency, their switching events may be phase-shifted so that theirswitching edges occur at advantageous times. Multi-phase converters maybe difficult to implement in microinverter applications. Withcoordination between the microinverters, such a configuration may beachievable. By the multi-phase technique, each converter switches at adesired frequency. The effective frequency of the combined outputs maybe higher when multiplied by the number of phased converters. Thisfeature allows filtering components to be smaller as their impedancesgenerally scale with frequency. Thus, use of filter components withinthe microinverters themselves and in the supervisor/controller (ifapplicable) may be improved.

Embodiments may also involve varying the switching frequencies of theconverters so as to create destructive interference among themicroinverters. This technique may be similar to the multi-phasetechnique, but is targeted toward reducing electromagnetic interference(EMI). In other words, the frequencies of each microinverter may bedifferent so that no concentration of noise occurs at one particularfrequency. The frequency and the phase selection may be designed so thatone microinverter may cancel components of noise of another. In effect,the supervisor/controller would assign frequencies and phase shift toeach microinverter to achieve a desirable result.

In some embodiments, an AC module system is employed. The AC modulesystem includes a plurality of ACPV branch circuits. The AC modulesystem may also include a PV supervisor/controller coupled to theplurality of ACPV branch circuits to aggregate power from the branchcircuits. The PV supervisor/controller may be configured to perform anonredundant operation function for each of the ACPV branch circuits.The performance of the nonredundant operational function may require anexchange of ACPV operational data between the ACPV branch circuits andthe PV supervisor/controller. The AC module system may also include amain service panel to receive aggregated power from the PVsupervisor/controller via a main line. The AC module system may alsoinclude a gateway device located within the PV supervisor/controller topermit control of the operational functions of each of the plurality ofACPV branch circuits. The control is preferably capable of beingperformed apart from the PV supervisor/controller.

In embodiments, a PV supervisor/controller from an AC module system mayalso be employed. The PV supervisor/controller may include cableconnections to ACPV branch circuits, a main power line to receive powerfrom the cable connections, and a gateway device to monitor the powerand to communicate using communication wires connected to the cableconnections and a surge suppressor coupled to the main power line. ThePV supervisor/controller may still further include a filter on the mainpower line and a power supply to supply power to the photovoltaic branchcircuits through the communication wires.

In embodiments, a method for generating power within an AC module systemmay be provided. The method may include receiving power signals from aplurality of ACPV branch circuits at a PV supervisor/controller wherethe PV supervisor/controller may be coupled to a main service panel viaa main line. The method may also include aggregating the power signalswithin the PV supervisor/controller, filtering the power signals in thePV supervisor/controller, and detecting information about the powersignals using a gateway device within the PV supervisor/controller.Nonredundant operational instructions for the PV branch circuits may becommunicated to the PV branch circuits using the PVsupervisor/controller in embodiments.

FIG. 1 depicts an AC module system 100 having a supervisor/controller108 according to some embodiments. System 100 includes main servicepanel 102 that collects power generated from one or more branch circuits104 and delivers it to one or more loads 106. A branch circuit may referto a PV module having a solar panel and a microinverter as well asseveral solar panels and a microinverter. As shown in FIG. 1, branchcircuits 104 a and 104 b deliver power, but any number of branchcircuits may be included. Further, branch circuits 104 may be rated atgreater than 3.84 kiloWatts (kW) each. Loads 106 include load 106 a andload 106 b, but any number of loads may be connected to main servicepanel 102.

PV supervisor/controller 108 is coupled between branch circuits 104 andmain service panel 102. PV supervisor/controller 108 may aggregate powerfrom branch circuits 104. PV supervisor/controller 108 may also performoperational functions for each of the branch circuits, as disclosed ingreater detail above and below. Using cables 105, PVsupervisor/controller 108 exchanges operational data with branchcircuits 106. PV supervisor/controller 108 may perform operations thatreplace or mirror operations done by the microinverters within eachbranch circuit 104.

Power is received from branch circuits 104 over cables 105 to power bus119 in PV supervisor/controller 108. Preferably, cables 105 are ACcables that deliver about 20 amps of current from the microinverterslocated in each branch circuit 104. Power bus 119 delivers theaggregated power, or current, to main line 109. Main line 109 deliversthe aggregated power to main service panel 102, which distributes thepower to loads 106.

PV supervisor/controller 108 also monitors this process and providescontrol operations on the power collection as well as the functions ofbranch circuits 104. Although the term “supervisor” is used with regardsto disclosed embodiments, the components also may act as a controller asindicated by the shared term supervisor/controller used herein. Thus, PVsupervisor 108 may have passive or active monitoring control withinsystem 100. PV supervisor 108, therefore, may be considered a power andcontrol hub between branch circuits 104 and main service panel 102. PVsupervisor 108 may include a certain topology, disclosed below, andcentralization of functionality. As will be shown, the disclosedembodiments may remove redundant operations performed in themicroinverters and place them in PV supervisor 108.

PV supervisor 108 also includes gateway device 116. Gateway device 116may perform gateway functions, such as overcurrent protection and branchcircuit aggregation. Gateway device 116 may perform algorithms andoperations to optimize power generation on branch circuits 104. As such,it receives data and power from each branch circuit 104 via connection120. Gateway device 116 also may communicate with the microinverterswithin branch circuits 104. Centralized server 114 also communicateswith gateway device 116 via connection 118. Connection 118 may be wiredor wireless connection over a network, such as the Internet using arouter. Gateway device 116 and server 114 may exchange information aboutbranch circuits 104, system 100, and PV supervisor 108 as well as otherinformation.

PV supervisor 108 also includes logic circuitry 121. Logic circuitry 121may include processors, memory storage, and other components to receiveinformation along with gateway device 116 to perform operations withinbranch circuits 104. These operations may be disclosed in greater detailbelow. Logic circuitry 121 may be coupled between power bus 119 andgateway device 116. Alternatively, the logic circuitry may beincorporated into gateway device 116.

In other embodiments, gateway device 116 may be a separate componentfrom PV supervisor 108. In this instance, gateway device 116 connects toPV supervisor 108 to receive information about aggregated power and toexchange data with the microinverters as well as server 114.

Other components in system 100 include service box 110 and meter 112.Additional components may be incorporated, though not shown. In someembodiments, PV supervisor 108 is incorporated into main service panel102. PV supervisor 108 and gateway device 116 may be located in thepanel. Alternatively, PV supervisor 108 may be located closer to branchcircuits 104, especially if the branch circuits receive power from thePV supervisor.

FIG. 2 depicts a branch circuit 106 having a PV module 202 andmicroinverter 204 according to some embodiments. The components shown inFIG. 2 are an example topology. Other topologies may be used for branchcircuits 106, including those with different components. A chassis 222may enclose one or more of PV module 202 and microinverter 204.

Microinverter 204 is coupled to a PV module 202. PV module 202 may be asolar panel that collects solar energy and converts it into power.Preferably, the power is DC power. The power is received by input stage206, which also may be known as a boost stage. Preferably, input stage206 may be a resonant DC-DC bridge circuit. Input stage 206 may convertthe received power to a high voltage, with electrical/transformerisolation provided by AC transformer 216. Input stage 206 also mayconduct maximum power point tracking (MPPT). In some embodiments, inputstage 206 may provide the converted voltage to a high voltage DC bus 207or to an active filter stage 214. In yet further embodiments, highvoltage DC bus 207 may be a 400 volt DC bus. High voltage DC bus 207 maybe known as a high ripple bus.

Output stage 208 converts the high voltage to a grid compatible ACcurrent that is output through cable 105, disclosed above. The highvoltage may be on high voltage bus 207. Output stage 208 also is coupledto AC transformer 216. Output stage 208 may be a resonant AC-AC bridgecircuit. Output stage 208 also may be coupled to filter 218, whichreceives the output current to reduce electrical distortion. Filter 218may include passive components, such as inductors and capacitors, toreduce the distortion. The distortion may be in the form of lowfrequency harmonics or high frequency interference.

Microinverter 204 also includes housekeeping power supply (HKPS) 210 toprovide stable voltage to logic and circuitry within the microinverter.More than one HKPS 210 may be implemented. Each HKPS 210 may have morethan one output voltage. In some embodiments, microinverter 204 may notinclude a HKPS 210 at all, and, instead, receives power from PVsupervisor 108 over cable 105. HKPS 210 also should be able to operatefrom a relatively high voltage from the panel voltage or the highvoltage bus 207 but regulate down to as little as 1 volt or less.

Microcontroller/digital signal processing circuit (Micro/DSP) 212 mayconduct most or all of the control functions for microinverter 204. Suchfunctions may include dynamic regulation of signals and regulatoryfunctions. Micro/DSP 212 may receive power from HKPS 210. In the absenceof a HKPS 210, then micro/DSP 212 may receive power from PV supervisor108.

An active filter stage 214 may be coupled to output stage 208. Activefilter stage 214 serve to decouple the high voltage capacitor 207 fromother voltages in the microinverter 204. Active filter stage 214 mayinclude a resonant AC-DC bridge circuit and may receive information andinstructions from micro/DSP 212.

Powerline carrier (PLC) circuit 220 may include circuits dedicated toproviding communications to and from PV supervisor 108 though wireswithin cable 105. PLC circuit 220, therefore, may be a communicationcircuit for microinverter 204. Cable 105 includes wires and connectorsfor connecting the AC output of microinverter 204 to PV supervisor 108.Alternatively, cable 105 may connect to another microinverter or chainof microinverters that eventually connect to PV supervisor 108.

Microinverter 204 also may include a surge suppressor 224. Surgesuppressor 224 may be coupled to output filter 218. In some embodiments,surge suppressor 224 may be partially embedded in filter 218. Surgesuppressor 224 includes circuitry to protect against high voltage surgeson the AC line. Surge suppressor 224 may provide surge protection thatcauses microinverter 204 to survive thousands of voltages in excess ofnormal line voltage. The circuitry of surge suppressor 224 may comprisemetal-oxide varistors (MOVs).

FIG. 3 depicts an example topology for PV supervisor 108 according tosome embodiments. PV supervisor 108, as shown in FIG. 1, includesgateway device 116 and logic circuitry 121. It also receives power frombranch circuits 104 through cables 105. Cables 105 may be connected toPV supervisor 108 by connectors 302. The AC current is received atcircuit breakers 304. Circuit breakers 304 may be 20 amp breakers. Inaddition, power connections 306 supply the current, which may be about16 amps (i.e., 80% of breaker rating) as well as other values, tocircuit breakers 304.

One or more additional components may be included in PV supervisor 108to provide additional operational features. In some instances, thesefeatures replace similar functionality within microinverters 204. Thismay eliminate or reduce redundant components throughout themicroinverters. In turn, the removal of redundant components may reducecosts of implementing system 100.

One such function may be surge suppression. PV supervisor 108 mayinclude surge suppressor 310. Surge suppressor 310 may be coupled tomain line 109 via power bus 119. In other embodiments, surge suppressor310 may be coupled directly to main line 109. Surge suppressor 310provides surge protection for microinverters 204 coupled to PVsupervisor 108. Surge suppressors 224 in microinverters 204 may beremoved or reduced to eliminate redundancy in system 100.

Another refinement may be to a combine high-speed communication linewith cables 105 leading to microinverters 204. Thus, communication wires308 may be included. Communications wires 308 may connect to gatewaydevice 116 and other components within PV supervisor 108. In someembodiments, communication wires 308 are bundled with the AC power wireswithin cables 105. Drop cables 309 from a rooftop may be run alongsidecommunication wires 308. Use of drop cables 309 may be an alternative toPLC communications, which is susceptible to line noise and numeroustroubleshooting tasks. Another physical layer, such as RS-485, may alsobe used. Preferred physical layers may be immune from noise, for themost part, as well as provide a faster response. Moreover, certainphysical layers, such as those employing RS-485, may be more reliableand have more inherent security.

The bundle of communication wires 308 with cables 105, and with orwithout drop cables 309, may allow PV supervisor 108 to deliver power tomicroinverters 204. Power supply 312 is included for these embodiments.In some embodiments, power supply 312 may replace HKPS 210 withinmicroinverters 204. Branch circuits 104 may be built without the need toinclude power supplies to provide power to logic circuits andcomponents. This may reduce the need to convert the relatively highpower going into a HKPS 210 into a smaller voltage signal. Power supply312 is shown as a standalone unit but may be integrated with gatewaydevice 116.

In embodiments, power supply 312 may be used in conjunction with thehousekeeping power supplies within microinverters 204. In suchinstances, when adequate power is not available at a branch circuit 104due to low sunlight or other low power conditions, power supply 312 mayprovide power via communication wires 308 to accommodate the powerrequirements. The power supplied to microinverters 204 under such ascenario may only power certain subcircuits or operate for a smallamount of time. HKPSs 210 may be reduced to simpler circuits, such as apostregulator or point-of-load circuit. In this instance, communicationwires 308 may be twisted pair or Ethernet cables or other suitablewiring approach to send the power.

Gateway device 116 may monitor power received from each branch circuit104 to determine when a low power condition exists. It may instructpower supply 312 to provide power to microinverters 204. Logic circuitry121 may also help in this analysis. Such a feature may be useful toinstallers attempting to communicate with the branch circuits in a lowpower situation. Further, if server 114 requests information on a branchcircuit 104 via gateway device 116, then the gateway device may “wakeup” the branch circuit to provide the information by providing the powerfrom power supply 312.

In some embodiments, reactive power may be injected into branch circuits104. If PV supervisor 108, using power supply 312, can provide enoughpower to power microcontrollers 204, then it may be able to provide thereactive power into branch circuits 104. The reactive power may includecurrent that is about 90 degrees out of phase with the voltage. Thus, PVsupervisor 108 may change the phase of the current or voltage of poweronto the grid. The disclosed embodiments may use the different phases toidentify and correct problems, as disclosed in greater detail below.Moreover, by using power supply 312, injection of reactive power mayoccur at night. Thus, one may schedule such tests and maintenance in theevening. For example, server 114 may instruct gateway device 116 tocommunicate to power supply 312 to inject the reactive power at timeswhen power is not being generated by branch circuits 104. This may avoidproblems of injecting power out of phase during the day when power isbeing generated.

Use of power supply 312 may eliminate or reduce redundancy withinmicroinverters 204. Each microinverter 204 will not need a full powersupply. Further, power supply 312 may be made more efficient and lesscosts sensitive than each HKPS 210 within each microinverter 204. PVsupervisor 108 also includes more space to fit a larger power supply312. Power supply 312, therefore, need not be particularly efficient,highly performing, or have a substantial power rating.

Filter 314 may be included in PV supervisor 108 to replace filters 218within microinverters 204. This feature eliminates or reduces redundancyas the aggregated function of filtering is performed centrally. Filter314 may be located on the output of main line 109 to filter the signalbefore it is delivered to main service panel 102. Alternatively, one ormore filters 314 may be located with circuit breakers 304.

Filter 314 may reduce lower frequency distortion or higher frequencynoise. Filter 314 also may selectively block some frequencies, such as achosen PLC frequency like 110 kHz used in some microinverters. Actually,PLC filtering may not be needed as communications using PV supervisor108 may be conducted with a hardwired connection. Thus, use of filter314 may reduce this need of filtering within system 100.

One or more sensors 316 may be included in PV supervisor 108. In someembodiments, sensors 316 may be coupled to the input and output offilter 314 to test and correct the filter. In some embodiments, sensors316 may be current transformers, but voltage, temperature, and othertypes of sensors may be used. In fact, other sensors 316 may be coupledto other components within PV supervisor 108, especially if filter 314is not present.

Gateway device 116 or logic circuitry 121 may receive the data collectedby sensors 316. These devices may use the data to monitor PV productionand home energy consumption. In some embodiments, sensors 316 areintegrated with PV supervisor 108 and may not require a separateinstallation, which may reduce extra work. Further, sensors 316 maycollect and provide data that improves the performance of system 100 andbranch circuits 104.

For example, sensors 316 may be used to improve the harmonic performanceof system 100. In such an example, microinverters 204 may have reducedfiltering if filter 314 is implemented. Thus, it may be more difficultfor the microinverters to monitor and correct for distortion. Gatewaydevice 116, however, may sense the collected PV current and, possibly inconjunction with logic circuitry 121, calculate the appropriatepredistortion or other correction signal to be used by microinverters204. Such information may be provided by communication wires 308. Thisfeature may be useful because varying number of microinverters 204 maybe installed with PV supervisor 108, thereby causing a wide range ofconditions to be encountered.

Sensors 316 also may be used for current limiting, fault detection, orcomplying with requirements such as those from regulatory agencies. Forexample, limits on power output may be required due to net exportlimitations. In this instance, PV supervisor 108 may cause, viacommunication wires 308, microinverters 204 to disable their poweroutput, curtail their power output, or otherwise alter behavior whendetecting a current that is out of range or otherwise unsuitable.Various limits may be established and checked against by PV supervisor108 using one or more sensors 316.

Most of the above examples pertain to branch circuits that are ACmodules. The disclosed embodiments, however, may be extended to othergenerating units, such as gas generators or grid-interactive storagedevices. Additional circuit breakers 304 may be added to accommodatemore generators. Further, circuit breakers 304 are depicted, but anysuitable overcurrent protection means can be used, especially as circuitbreakers may be physically large or costly. For example, a sensor 316with detection circuitry may be used to sense an overcurrent. Byaugmenting some or all of the (previous) breaker lines with controlledswitches, such as relays, the current may be interrupted without using acircuit breaker.

In some embodiments, gateway device 116 or logic circuitry 121 mayprovide the sensing and calculation to determine the phase angle of thepower lines from branch circuits 104. Every microinverter 204 maycalculate the phase angle of the power line, such as cable 105. With PVsupervisor 108, high speed communication with microinverters 204 may beimplemented.

The determination of the phase angle normally may be done withphase-locked loop (PLL) circuits. These circuits may be placed in eachmicroinverter 204. This aspect may be computationally intensive,especially in consideration of highly-distorted line voltages. Thus, thecomputation burden for microinverters 204 may be reduced byconsolidating the PLL function in PV supervisor 108. PV supervisor 108may provide via communication wires 308 a synchronizing signal by whichall microinverters 204 would base their own phase angles. For example,in the United States, synchronization would be to the 60 Hz power line.

In embodiments, a deeper level of synchronization may be achieved. Thehigh frequency switching outputs of microinverters 204 may besynchronized, though not necessarily simultaneous. High-frequencymodulation signals may be outputted, often pulse width modulation. Sometopologies use a fixed-frequency modulation or one that is fixed forsome period of time or under some operating conditions. The disclosedembodiments may use communication wires 308 to coordinate the switchingof microinverters 204 to generate overall higher performance or lowercost.

Thus, if two or more converters are switching at the same frequency, theswitching events may be phase-shifted so that the switching edges occurat advantageous times. Multi-phase converters may be difficult toimplement in microinverter applications. With coordination between themicroinverters, such implementation may be achieved. By the multi-phasetechnique, each converter may switch at a desirable frequency. Theeffective frequency of the combined outputs may be higher, as multipliedby the number of phased converters. This allows filtering components tobe smaller as the impedances generally scale with frequency. This mayreduce cost of filter components in microinverters 204 or filter 314 inPV supervisor 108.

Thus, the effective frequency seen by PV supervisor 108 may increase bythe number of microinverters 204. This increase may shrink the size offilter 314 or the filters in microinverters 204. It also may allow forthe cancellation of harmonics as amplitudes may be phase shifted. Forexample, in system 100 of 10 microinverters 204, the even numberedinverters may have a phase shift of 0 degrees while the odd numberedinverters may have a phase shift of 180 degrees.

In some embodiments, the switching frequencies may be varied so as tocreate destructive interference among microinverters 204. This featuremay be similar to the multi-phase technique, but is more targeted towardreducing electromagnetic interference (EMI). The frequencies ofmicroinverters 204 may be different so that there is no concentration ofnoise at one particular frequency. The frequency and phase selection maybe designed so that one microinverter 204 can cancel components of noiseof another microinverter. Thus, PV supervisor 108 may assign frequenciesand phase shift to each microinverter 204 to achieve a desired result.For example, one microinverter may produce +1 volt of noise whileanother microinverter produces −1 volt of noise. The microinverters alsomay be allowed to produce more noise than usual. Control signals may besent to microinverters 204 via communication wires 308.

PV supervisor 108 also includes battery or energy storage device 318. Aspower is aggregated in PV supervisor 108, some may be stored in device318. In other embodiments, more than one storage device 318 may beimplemented. As can be seen, battery/storage 318 may be coupled to powersupply 312 via charging circuit 319. Charging circuit 319 may protectbattery 318 and comprise a diode, capacitor, switch and the like.

FIG. 4 depicts a flowchart 400 for generating power within system 100according to some embodiments. Reference may be made to elements shownin FIGS. 1-3 for illustrative purposes. The embodiments herein are notlimited to the topologies shown in these figures.

Step 402 executes by generating power within branch circuits 104 ofsystem 100. Branch circuits 104 may be PV modules that generate powerfrom received solar energy. Branch circuits 104 may convert this energyinto a power signal, such as a current, that is output from each circuitto PV supervisor 108.

Step 404 executes by receiving the power signals from branch circuits104 at PV supervisor 108. Cables 105 may connect to PV supervisor 108from each branch circuit 104. The signals may flow through circuitbreakers 304 to power bus 119. Step 406 executes by aggregating thepower signals with PV supervisor 108. PV supervisor 108 is coupled tomain service panel 102 via main line 109.

Step 408 executes by filtering the aggregated power signals in PVsupervisor 108 using filter 314. In some embodiments, filter 314 may beremoved and filtering performed in microinverters 204 of branch circuits104. Step 410 executes by supplying the aggregated power to main servicepanel 102 over main line 109.

Step 412 executes by detecting information about the power signals usinggateway device 116 within PV supervisor 108. One or more sensors 316 maybe used to detect information about the signals. Alternatively, gatewaydevice 116 may receive individual power signals directly. As disclosedabove, such information may include frequency, noise, phase shift,amplitude, and the like. Gateway device 116 or logic circuitry 121 mayuse this information to determine a status for the power signals, asexecuted in step 414.

Step 416 executes by communicating the instructions for branch circuits104 to the branch circuits using PV supervisor 108. In some embodiments,the instructions are nonredundant operational instructions in that theyare instructing or providing functions to microinverters 204 that arenot being done at the microinverters. Using the status of the receivedpower signals, PV supervisor 108 may determine some action needs to betaken and communicates to microinverters 204 using communication wires308. Examples of instructions are disclosed above.

Step 418 executes by providing power to microinverters 204 from PVsupervisor 108. Power supply 312 may be used to provide power to themicroinverters when it is determined that a low power condition isoccurring. Other actions may require power to be supplied from PVsupervisor 108, as disclosed above.

FIGS. 5 to 9 depicts example embodiments of PV supervisor 108 coupled tobranch circuits 104. These figures may show example topologies used byPV supervisor 108. As a result of these topologies, the componentswithin branch circuits 104 may change. Components within PV supervisor108 shown in FIGS. 5 to 9 are disclosed above, and, are not necessarilyrepeated in the description below.

FIG. 5 depicts illustrates PV supervisor 108 connected to branchcircuits 104 (photovoltaic modules) as may be employed in someembodiments. PV supervisor 108 includes gateway device 116 havingconnections 118 and 120. Gateway device 116 may communicate with branchcircuits 104. PV supervisor 108 aggregates power from branch circuits104 to deliver to main service panel 102 using main line 109.

PV supervisor 108 also includes surge suppressor 310. As shown, surgesuppressor 310 is coupled to power 119. As disclosed above, surgesuppressor 310 may be preinstalled in PV supervisor 108 to protect thebranch circuits. As a result, branch circuits 104 may have theirrespective surge suppressors (shown as surge suppressor 224 in FIG. 2)removed. This feature reduces redundancy within the branch circuits andpossibly lowers costs.

FIG. 6 depicts PV supervisor 108 connected to branch circuits 104 as maybe employed in some additional embodiments. PV supervisor 108 includessurge suppressor 310 and gateway device 116, along with other componentsto collect and monitor power from branch circuits 104. PV supervisor 108also includes a communication capability to communicate with the branchcircuits.

In these embodiments, gateway device 116 may exchange data with branchcircuits 104 using communication wires 308. As noted above,communication wires 308 may be bundled with AC cables 105 to attach toeach branch circuit 104. As disclosed above, various suitable physicallayers may be employed including PLC transmit and receive circuits andRS-485 communication standards to provide communication capabilities andphysical layer support to these communications.

FIG. 7 depicts PV supervisor 108 connected to branch circuits 104 as maybe employed in some additional embodiments. PV supervisor 108 includespower supply 312. As shown, power supply 312 may be a standalone unitor, alternatively, may be integrated with gateway device 116.

As disclosed above, power supply 312 may supply power to branch circuits104 via the same hardwired bundle as communication wires 308. Branchcircuits 104 also may have one or more of their housekeeping powersupplies (shown as housekeeping power supply 210 in FIG. 2) eliminatedor significantly reduced. Thus, this feature also may eliminate orreduce redundancy within branch circuits 104.

FIG. 8 depicts PV supervisor 108 connected to branch circuits 104 as maybe employed in some additional embodiments. PV supervisor 108 includesfilter 314. As disclosed above, some or all of the filter components maybe removed from branch circuits 104. Filter 314 is shown connected tomain line 109 but the filter components also may be placed at circuitbreakers 304. As with the other embodiments, filter components withinbranch circuits 104 may be eliminated or reduced to rid the branchcircuits of redundancy.

FIG. 9 depicts PV supervisor 108 connected to branch circuits 104 as maybe employed in some additional embodiments. PV supervisor 108 includesone or more sensors 316. As shown, sensors 316 are located at the inputand output of filter 314, but may be located elsewhere within PVsupervisor 108, especially if a filter is not used therein. For example,sensors 316 may be located on main line 109 or to circuit breakers 304.Gateway device 116 may obtain data about the power being aggregatedwithin PV supervisor 108 using sensors 316. As shown in FIG. 9, sensors316 may be coupled directly to gateway device 116.

Although specific embodiments have been described above, theseembodiments are not intended to limit the scope of the presentdisclosure, even where only a single embodiment is described withrespect to a particular feature. Examples of features provided in thedisclosure are intended to be illustrative rather than restrictiveunless stated otherwise. The above description is intended to cover suchalternatives, modifications, and equivalents as would be apparent to aperson skilled in the art having the benefit of this disclosure.

The scope of the present disclosure includes any feature or combinationof features disclosed herein (either explicitly or implicitly), or anygeneralization thereof, whether or not it mitigates any or all of theproblems addressed herein. Accordingly, new claims may be formulatedduring prosecution of this application (or an application claimingpriority thereto) to any such combination of features. In particular,with reference to the appended claims, features from dependent claimsmay be combined with those of the independent claims and features fromrespective independent claims may be combined in any appropriate mannerand not merely in the specific combinations enumerated in the appendedclaims.

What is claimed is:
 1. An alternating current (AC) module systemcomprising: a plurality of AC photovoltaic (PV) branch circuits; a PVcontroller coupled to the plurality of ACPV branch circuits to aggregatepower from the branch circuits, the PV controller configured to performa nonredundant operational function for each of the ACPV branchcircuits, the performance of the nonredundant operational functionrequiring an exchange of ACPV operational data between the ACPV branchcircuits and the PV controller; and a gateway device located within thePV controller to permit control of the operational functions of each ofthe plurality of ACPV branch circuits, the control capable of beingperformed apart from the PV controller.
 2. The AC module system of claim1, further comprising a main service panel to receive aggregated powerfrom the PV controller via a main line; and a surge suppressor locatedwithin the PV controller to provide surge protection for the main line.3. The AC module system of claim 2, wherein the plurality of ACPV branchcircuits do not include a surge suppressor.
 4. The AC module system ofclaim 1, further comprising a plurality of AC cables connected to theplurality of ACPV branch circuits, wherein a plurality of communicationwires is bundled with the plurality of AC cables, the plurality ofcommunication wires coupled to the PV controller.
 5. The AC modulesystem of claim 4, further comprising a plurality of drop cables bundledwith the plurality of communication wires.
 6. The AC module system ofclaim 1, further comprising a power supply located within the gatewaydevice to supply power to the plurality of ACPV branch circuits.
 7. TheAC module system of claim 6, wherein the power is provided from thepower supply over a plurality of communication lines coupled to theplurality of ACPV branch circuits.
 8. The AC module system of claim 6,wherein the plurality of ACPV branch circuits do not includehousekeeping power supplies.
 9. The AC module system of claim 6, whereinthe power supply is integrated with the gateway device.
 10. The ACmodule system of claim 6, wherein the power supply is controlled by thegateway device to provide power to the plurality of ACPV branchcircuits.
 11. The AC module system of claim 1, further comprising afilter located within the PV controller, wherein the filter is coupledto a main line and to the main service panel.
 12. The AC module systemof claim 1, further comprising one or more sensors located on the mainline in the PV controller.
 13. The AC module system of claim 12, whereinthe one or more sensors is a current transformer sensor.
 14. The ACmodule system of claim 12, wherein the gateway device controls thefunction on the plurality of ACPV branch circuits using information fromthe one or more sensors.
 15. A photovoltaic (PV) controller for analternating current (AC) module system, the PV controller comprising:cable connections to alternating current (AC) photovoltaic (PV) branchcircuits; a main power line to receive power from the cable connections;a gateway device to monitor the power and to communicate usingcommunication wires connected to the cable connections; a surgesuppressor coupled to the main power line; a filter on the main powerline; and a power supply to supply power to the photovoltaic branchcircuits through the communication wires.
 16. The PV controller of claim15 wherein the PV controller is configured to perform a nonredundantoperational function for one or more ACPV branch circuits, theperformance of the nonredundant operational function requiring anexchange of ACPV operational data between the ACPV branch circuits andthe PV controller.
 17. The PV controller of claim 15, further comprisingone or more sensors coupled to the main power line to provide feedbackto the gateway device.
 18. The PV controller of claim 15, wherein thegateway device includes an antenna for wireless communication over anetwork.
 19. A method for generating power within an alternating current(AC) module system, the method comprising: receiving power signals froma plurality of AC photovoltaic (PV) branch circuits at a PV controller,wherein the PV controller is coupled to a main service panel via a mainline; aggregating the power signals within the PV controller; filteringthe power signals in the PV controller; detecting information about thepower signals using a gateway device within the PV controller; andcommunicating nonreduntant operational instructions for the PV branchcircuits to the PV branch circuits using the PV controller.
 20. Themethod for generating power of claim 19 further comprising: performingphase lock loop operations using the power signal for reduction of noisein a frequency band.